Air mattresses are used with cots and beds to provide yieldable body supports. The air mattresses are air-filled bags having flexible, air impervious sheet members secured together to form one or more longitudinal chambers for accommodating air under pressure. Air mattresses have air inlet tubes that are used with hand-operated pumps, bag pumps, and other sources of air under pressure to inflate the mattresses. Plugs are used to close the tubes after the mattresses are inflated with air. Conventional air mattresses do not have pressure relief valves so that they can be easily over-inflated, causing rupture of the mattress material or the separation of the seams. An over-inflated air mattress is relatively hard and can become misshaped and wobbly.
Walker in U.S. Pat. No. 4,644,597 discloses an air mattress with an air pressure relief valve to prevent over-inflation of the mattress The mattress has transverse webs secured to top and bottom walls and opposite side walls to provide transverse air chambers. The opposite ends of the webs are not secured to the top and bottom walls to provide openings to allow air to flow between the chambers. This eliminates holding of the top and bottom walls longitudinally along the opposite sides thereof so that opposite side portions of the top and bottom walls bulge or deform outwardly when the mattress is filled with air under pressure. This concentrates pulling forces on the ends of the seams that connect the webs to the top and bottom walls. These forces are sufficient to cause the seams to separate with the result of a one or more large transverse humps in the air mattress. When two air mattresses are placed side-by-side to make a double or queen size bed, there are two longitudinal humps or ridges down the middle of the bed and a longitudinal hump along each side of the bed. This is an undesirable feature in an air bed. The air mattress is connected to an air pump operable to supply air to the air mattress through a tube connected to an end of the air mattress. An air pressure relief valve is mounted in the same end as the air inlet tube. The remote end of the air mattress is completely enclosed so that when the air mattress is under a moving or sudden load, such as a person's shifting weight or roll-over weight, the air pressure in the remote end of the air mattress substantially increases. This sudden increase in air pressure in the remote end of the air mattress can cause seam tear and separation and even rupture of the walls of the air mattress.